In thermal power generation facilities and boiler equipment, a large amount of fuels such as coal and heavy oil are burned, generating a large amount of carbon dioxide. In recent years, it has been proposed that discharge of carbon dioxide (CO2) should be globally controlled in view of air pollution and global warming. As one of the techniques for separation and recovery of CO2, known is a method of absorbing CO2 into absorbent such as an amine compound, i.e., a chemical absorption method. This chemical absorption method requires a large amount of thermal energy. In the chemical absorption method, among total energy generated from combustion, energy that can be used for the original purposes such as power generation will be decreased, resulting in reduction of power generation efficiency. From an economical point of view, it is important to suppress the decrease in power generation efficiency to effectively utilize the thermal energy in equipment where the chemical absorption method is used.
As an approach for increasing thermal efficiency, for example, Patent Literature 1 discloses a method of purifying combustion exhaust gas comprising: contacting the combustion exhaust gas with absorbent in a CO2 absorption column to absorb CO2 in the combustion exhaust gas into the absorbent, the absorbent comprising an aqueous alkanolamine solution; applying heat contained in the combustion exhaust gas and heat of condensation of liquid vapor in the combustion gas to the CO2 absorbed absorbent in a heat exchanger; heating the CO2 absorbed absorbent in a desorption column and releasing CO2 to regenerate the absorbent and then circulating the regenerated absorbent to the CO2 absorption column.
Further, in the section of BACKGROUND ART and FIG. 7 of Patent Literature 1, disclosed is a combustion exhaust gas purifying equipment comprising a boiler, an electrostatic precipitator, a blower, a desulfurization device, a CO2 absorption column, a CO2 releasing desorption column and the like, wherein a gas/gas heater is provided between a line connecting the blower and the desulfurization device and a line connecting the absorption column and a chimney.
Further, Patent Literature 2 discloses flue gas treatment equipment in which a dust precipitator and a desulfurization device for treating smoke, dust and sulfur oxides contained in exhaust gas from a boiler are arranged in sequence from the upstream of an exhaust gas flow line, comprising a heat recovery device provided at the exhaust gas flow line between the precipitator and the desulfurization device, and a feed water line for supplying water to the boiler and a feed water heater provided at the feed water line, and an interconnecting line for heat medium circulation interconnecting the heat recovery device and the feed water heater.
Patent Literature 1: JP H7-241440 A
Patent Literature 2: JP 2001-239129 A